The basics of dog nutrition – water-soluble vitamins

Vitamin B1 (Thiamin)
After being modified in the body, thiamine pyrophosphate is involved in the following processes: Carbohydrate Metabolism, neurotransmitter production of glucose derivatives, and lipid metabolism. Important for growing dogs, nursing bitches, and working dogs.
Sources: Wheat Germs (2.4 mg / 100 g).

Vitamin C (Ascorbic acid)
There is no need for a vitamin C supplement as the dog synthesizes sufficient amounts of it in his liver and kidney. Even experiments, where vitamin C was supplemented to avoid conditions on the skeleton (e. g. HD) proved unsuccessful. Only after major surgery, serious burn wounds, liver diseases, or serious infections a supplement may be useful.
Sources: Acerola (1700 mg / 100 g), rose hip (1250 mg / 100 g), parsley (160 mg / 100 g).

Conclusion: If your vet told you that your dog needs a supplement of the Vitamin B group you may add 50 g of beef liver and one raw egg yolk per week as well as one table spoon of wheat germs per day to the usual food ration.